Some gall stones do float. The ones that float are made of cholesterol. Flushing the liver and gall bladder gets the stones out. You passed stones, that is what it was in the toilet. Flushing also gets the stones out of the liver, which is where they are formed. One flush is not enough. You need to keep doing it until no more stones are coming out.
To get out harder stones, which are made of calcium, you can take herbs that soften stones. You can drink a gallon of apple juice during the week before you flush. You can take malic acid to soften stones.